触发器 完美运行

 

CREATE TRIGGER  NO5 ON SC
FOR insert,delete,update
AS
declare @totalScore int
declare @score1 int
declare @score2 int
declare @credit int
declare @Cno char(4)
declare @Sno char(10)

select @score1=l.Grade from inserted l
select @score2=l.Grade from deleted l/*修改时删掉的那个分数*/
select @Cno=l.Cno from inserted l
select @Sno=l.Sno from inserted l
if(@score1>=60)
begin
select @credit=Ccredit from Course where Course.Cno=@Cno
select @totalScore=(select totalScore from Student where Sno=@Sno)+@credit
update Student  set totalScore=@totalScore where Sno=@Sno
end

if update(grade)
begin
select @score2=l.Grade from inserted l
select @score1=l.Grade from deleted l/*修改时删掉的那个分数*/
select @credit=Ccredit from Course where Course.Cno=@Cno
select @Cno=l.Cno from inserted l
select @Sno=l.Sno from inserted l
if(@score1>60 and @score2<60)--把及格改成不及格
update Student set totalScore=totalScore-@credit where Sno=@Sno
else if(@score2>60 and @score1<60)--把不及格改成及格
update Student set totalScore=totalScore+@credit where Sno=@Sno
end